Cysteine- and histidine-rich domains (CHORDs) are 60-amino acid modules that bind two zinc ions. They are usually arranged in tandem and are found in all tested eukaryotes, with the exception of yeast, where they are involved in processes ranging from pressure sensing in the heart to maintenance of diploidy in fungi, and exhibit distinct protein-protein interaction specificity. Six cysteine and two histidine residues are invariant within the CHORD domain. Three other residues are also invariant and some positions are confined to positive, negative, or aromatic amino acids [1,2].

Some proteins known to contain a CHORD domain are listed below:

• Plant protein Required for Mla12 Resistance (RAR1), a common component in the signaling pathways triggered by many resistance (R) proteins.
• Caenorhabditis elegans CHORD containing protein (chp). It plays a vital role in germline development and embryogenesis.
• Vertebrate cysteine and histidine-rich domain-containing protein 1 (CHORD domain-containing protein 1), a target for transcriptional activation by heat-shock factor 1 (HSF1).
• Mammalian integrin β-1-binding protein 2 (melusin). It may play a role during maturation and/or organization of muscles cells.

The profile we developed covers the entire CHORD domain.